﻿#pragma once
#include <iostream>
#include <new>
#include <vector>
#include <unordered_map>
#include <thread>
#include <mutex>
#include <time.h>
#include <assert.h>

#ifdef _WIN32
#include <windows.h>
#else
//
#endif

using std::cout;
using std::endl;

static const size_t MAX_BYTES = 256 * 1024;
static const size_t NFREELIST = 208;        // 最大哈希桶的数量
static const size_t NPAGES = 129;           // 数组从0开始，页数最大是128
static const size_t PAGE_SHIFT = 13;

#ifdef _WIN64
typedef unsigned long long PAGE_ID;
#elif _WIN32
typedef size_t PAGE_ID;
#else
	// linux下
#endif

// 直接去堆上按⻚申请空间
inline static void* SystemAlloc(size_t kpage)
{
#ifdef _WIN32
	void* ptr = VirtualAlloc(0, kpage << PAGE_SHIFT, 
		MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
#else
	// linux下brk mmap等 
#endif
	if (ptr == nullptr)
		throw std::bad_alloc();
	return ptr;
}

static void*& NextObj(void* obj)
{
	return *(void**)obj;
}

inline static void SystemFree(void* ptr)
{
#ifdef _WIN32
	VirtualFree(ptr, 0, MEM_RELEASE);
#else
	// sbrk unmmap等
#endif
}


// 管理切分好的小对象的自由链表
class FreeList
{
public:
	void Push(void* obj)
	{
		assert(obj);

		// 头插
		NextObj(obj) = _freeList;
		_freeList = obj;
		++_size;
	}

	void PushRange(void* start, void* end, size_t n)
	{
		assert(start && end);

		NextObj(end) = _freeList;
		_freeList = start;

		int i = 0;
		void* cur = start;
		while (cur)
		{
			cur = NextObj(cur);
			++i;
		}

		if (n != i)
		{
			int x = 0;
		}

		_size += n;
	}

	void* Pop()
	{
		assert(_freeList);

		// 头删
		void* obj = _freeList;
		_freeList = NextObj(obj);
		--_size;

		return obj;
	}

	void PopRange(void*& start, void*& end, size_t n)
	{
		assert(_freeList);
		assert(n >= _size);

		start = _freeList;
		end = start;

		for (size_t i = 0; i < n - 1; ++i)
		{
			end = NextObj(end);
		}
		_freeList = NextObj(end);
		NextObj(end) = nullptr;
		_size -= n;
	}

	bool Empty(){ return _freeList == nullptr; }

	size_t& MaxSize(){ return _maxSize; }

	size_t Size() { return _size; }
private:
	void* _freeList = nullptr;
	size_t _maxSize = 1;      // 慢启动算法相关，一开始初始化为1
	size_t _size = 0;        // 插入对象的数量, 记得初始化
};

// 计算对象大小的对齐映射规则
class SizeClass
{
	//size_t _RoundUp(size_t size, size_t alignNum)
	//{
	//	size_t alignSize;
	//	if (size % alignNum != 0)
	//	{
	//		alignSize = (size / alignNum + 1) * alignNum;
	//	}
	//	else
	//	{
	//		alignSize = size;
	//	}
	//	return alignSize;
	//}
	//static inline size_t _Index(size_t bytes, size_t alignNum)
	//{
	//	if (bytes % alignNum == 0)
	//	{
	//		return bytes / alignNum - 1;
	//	}
	//	return bytes / alignNum;
	//}
	
	static inline size_t _Index(size_t bytes, size_t align_shift)
	{
		return ((bytes + (1 << align_shift) - 1) >> align_shift) - 1;
	}
public:
	static inline size_t _RoundUp(size_t bytes, size_t alignNum)
	{
		return ((bytes + alignNum - 1) & ~(alignNum - 1));
	}
	// 整体通知在最多10%左右的内碎片浪费
	// [1,128]                    8bytes对齐       freelist[0,16)
	// [128+1,1024]               16bytes对齐      freelist[16,72)
	// [1024+1,8*1024]            128bytes对齐     freelist[72,128)
	// [8*1024+1,64*1024]         1024bytes对齐    freelist[128,184)
	// [64*1024, 256*1024]        8*1024bytes对齐  freelist[184,208)

	static inline size_t Index(size_t bytes)
	{
		assert(bytes <= MAX_BYTES);

		//  每个区间有多少个链
		//static int group_array[4] = { 16, 16+56, 16+56+56, 16+56+56+56 };
		static int group_array[4] = { 16, 72, 128, 184 };
		if (bytes <= 128)
		{
			return _Index(bytes, 3);
		}
		else if (bytes <= 1024)
		{
			return _Index(bytes - 128, 4) + group_array[0];
		}
		else if (bytes <= 8 * 1024)
		{
			return _Index(bytes - 1024, 7) + group_array[1];
		}
		else if (bytes <= 64 * 1024)
		{
			return _Index(bytes - 8 * 1024, 10) + group_array[2];
		}
		else if (bytes <= 256 * 1024)
		{
			return _Index(bytes - 64 * 1024, 13) + group_array[3];
		}
		else
		{
			assert(false);
			return -1;
		}
	}
	static inline size_t RoundUp(size_t size)
	{
		if (size <= 128)
		{
			return _RoundUp(size, 8);
		}
		else if (size <= 1024)
		{
			return _RoundUp(size, 16);
		}
		else if (size <= 8 * 1024)
		{
			return _RoundUp(size, 128);
		}
		else if (size <= 64 * 1024)
		{
			return _RoundUp(size, 1024);
		}
		else if (size <= 256 * 1024)
		{
			return _RoundUp(size, 8 * 1024);
		}
		else
		{
			return _RoundUp(size, 1 << PAGE_SHIFT);
		}
	}
	// ⼀次从thread cache中⼼缓存获取多少个
	static size_t NumMoveSize(size_t size)
	{
		assert(size > 0);

		if (size == 0)
			return 0;
		// [2, 512]，⼀次批量移动多少个对象的(慢启动)上限值
		// ⼩对象⼀次批量上限⾼
		// ⼩对象⼀次批量上限低
		int num = MAX_BYTES / size;
		if (num < 2)
			num = 2;

		if (num > 512)
			num = 512;
		return num;
	}

	// 计算一次向系统获取几个页
	// 单个对象 8bytes
	// ...
	// 单个对象 256KB
	static size_t NumMovePage(size_t size)
	{
		size_t num = NumMoveSize(size);
		size_t npage = num * size;

		npage >>= PAGE_SHIFT;
		if (npage == 0)
			npage = 1;

		return npage;
	}
};

// 管理多个连续页的大块内存跨度结构
struct Span
{
	PAGE_ID _pageId = 0;  // 大块内存起始页的页号  
	size_t _num = 0;        // 页的数量

	Span* _next = nullptr;      // 双向链表结构
	Span* _prev = nullptr;

	size_t _objSize = 0;        // 切好的小对象的大小
	size_t _useCount = 0;       // 切好小块内存，被分配给thread cache的计数
	void* _freeList = nullptr;  // 切好小块内存的自由链表

	bool _isUse = false;           // 是否在被使用
};

// 带头双向循环链表
class SpanList
{
public:
	SpanList()
	{
		_head = new Span;
		_head->_next = _head;
		_head->_prev = _head;
	}

	Span* Begin()
	{
		return _head->_next;
	}

	Span* End()
	{
		return _head;
	}

	bool Empty()
	{
		return _head->_next == _head;
	}

	void Insert(Span* pos, Span* newSpan)
	{
		assert(pos);
		assert(newSpan);

		Span* prev = pos->_prev;   // 一开始赋值成pos，导致错误！！！
		// prev newSpan pos
		prev->_next = newSpan;
		newSpan->_prev = prev;
		newSpan->_next = pos;
		pos->_prev = newSpan;
	}

	void Erase(Span* pos)
	{
		assert(pos);
		assert(pos != _head);

		Span* prev = pos->_prev;
		Span* next = pos->_next;

		prev->_next = next;
		next->_prev = prev;
	}

	void PushFront(Span* span)
	{
		Insert(Begin(), span);
	}

	Span* PopFront()
	{
		Span* front = _head->_next;
		Erase(front);
		return front;
	}

private:
	Span* _head;
public:
	std::mutex _mtx; // 桶锁
};